Air bag devices that are equipped in a vehicle are placed at various locations inside the vehicle in order to adequately restrain a passenger according to various kinds of collisions.
For example, when a vehicle is in a rear-end collision accident, an air bag device for rear-end collision has been proposed that would protect a passenger from impact that is applied from the rear of the vehicle.
In ultra compact cars that have been developed in recent years, or in various kinds of minivan-type one-box cars, in order to maintain sufficient space inside the vehicle, the rearmost seat may be placed such that the seat back is located directly in front of the back door. In an ultra compact car, the rearmost seat may, for example, be a front seat that has been moved toward the rear. In a minivan having a layout with three rows of seats, the rearmost seat may be the third row of seats.
In a vehicle where the rearmost seat back is close to the back door in this way, when the vehicle is hit from behind by a moving vehicle at a speed of about 50 km/h, a passenger sitting in the rear seat moves toward the back of the seat (in the direction of the colliding vehicle), and may hit the back of his/her head on the rear window or the like in the rear-end section of the vehicle. In order to prevent such an accident, the use of an air bag device for rear-end collision is effective.
A conventional air bag device for rear-end collision is such that an air bag is housed in a folded state in an air bag housing space, which is a space between the rear-end section of the vehicle roof, for example the rear end of the roof panel, and the interior rear roof ceiling panel.
When a collision from the rear of the vehicle is detected, an inflator that is connected to the air bag operates and injects gas into the air bag. The injected air causes the air bag to inflate and expand in a curtain shape downward from the housing space in the roof toward the bottom of the vehicle cabin, covering the rear window. As a result, the air bag prevents a secondary collision with the rear window by the passenger that moves toward the rear.